Out of memory errors - Please Help

[severian]

When trying to backup a game using CDRWIN, I get "Hard disc full" error message, even though I have over a gig memory left. Occasionally I can click on the cleanup disc button which then clears the (empty) recycle bin and carries on copying the disc to hard drive. I may be lucky and be able to do this a couple of times and get the file downloaded but it usually just aborts.
I then have to run scandisc or even defrag to get everything back to normal.
This is driving me crazy. Any help will be most appreciated.